1. Field of the Invention
The subject of the present invention is a network for distributing information and its fault management process. It is mainly usable in the field of telecommunications, especially in aeronautics. This invention could equally well be applied to ground-based telecommunications networks or in any other field such as the marine sector. The aim of the invention is to allow an increase in a reliability of such a network. With the invention, one increases a fault resistance of a network. The fault management process associated with the invention makes it possible to increase the stability whilst increasing the robustness of the network (load holding), thereby making it possible to reduce a risk of collapse thereof (severing of transmissions for some of the users of this network).
2. Discussion of the Background
At present, IFE type (In Flight Entertainment) telecommunications networks are found in aircraft cabins. These telecommunications networks makes it possible to offer passengers intangible services such as video on demand, music, television, Internet connection or more generally to send inquiries to a central unit without moving. This central unit has the job of supplying data, associated with a corresponding function across the network. A function can thus be a broadcast on a terminal available to a passenger of a requested program, a telephone call, an order for a product (drink, purchasing of duty-free goods) or any other function able to travel over a telecommunications network. One method of construction commonly employed to construct such a distribution network consists in adopting a star topology with several levels, in particular according to ARINC standard 628 part 4A. In such a construction, a first level consists of a central unit to which are linked, according to a point-to-point mode, information splitting devices. Each information splitting device comprises several inputs/outputs. An input/output is linked to a terminal by way of a bus. There are as many terminals as passengers.
Such a construction exhibits problems. In practice, the airline companies and more generally the operators of such networks are very sensitive to the availability rates of these items of equipment, which condition the degree to which their lines and their apparatuses are frequented. Thus, upon a fault of the network between a terminal and a splitting device, access to the services from this terminal is impossible. Moreover, if the fault occurs in a splitting device, then all the terminals which are linked to this device are inaccessible. Generally, faults in a network arise out of very harsh climatic and environmental conditions (vibrations, shocks) to which elements of the network are subjected. In practice, in most cases such a network is constructed from hardware which is envisaged mainly for ground-based use. In this ground-based use, one generally has stable climatic conditions. By contrast, with an aircraft, the climatic conditions are highly unstable. Thus, before a departure, during an aircraft parking phase, one may have a temperature of greater than +60° C. During a flight the temperature decreases to a value of the order of −50° C. On-landing the temperature may be +40° for example. These sizeable temperature variations are detrimental to correct operation of the constituent hardware of the network. This results in a possibly high fault rate.
Moreover, upon a fault, users of these terminals are generally moved to other terminals accessible from the central unit. Such a movement has the effect of creating an imbalance of the aircraft. This imbalance is generally compensated for through an increase in the speed of one of the engines of the craft, resulting in an increase in fuel consumption.
A common solution for testing the correct operation of terminals consists in bringing in tester users whose job is to test the terminals before each use of the aircraft. However, this solution is very unwieldy to implement by reason of a sizeable number of tester users which it requires and of the time for which the aircraft is grounded. This entails an increase in a maintenance cost of such a network. This solution can be applied only when the craft is on the ground. That is to say one does not intervene at the time the fault occurs but afterwards. Moreover, this checking operation merely has the aim of cataloging the terminals or splitting devices which are nonoperational.